Mechanism and method for controlling sintering



July 13, 1965 r. R. scHuERGER ETAL 3,194,546

MECHANISM AND METHOD FOR CONTROLLING SINTERING v Filed Aug. 29. 1958 svsheets-sheet 1 .Su/lmalar [3l-gna] {c} TE: 1

Raf/o Y Con/rol Wafer Trimmer Bin Control Ratio Control I l /0/ Signal{b} /4 WI Summalar (S/gnd/ {a} 32 28 Sin/erin Mac/:ine a i 35 m @grrr-raug/r indicafar 9 Feedf f afe Grate speed campa/Img c/rcu/f conro/T/as /N V E N TOPS 7/1'0MA5` R. SCHUERGER and Aller/rey MECHANISM ANDMETHOD FOR CONTROLLING SINTERING Filed Aug. 29. 1958 July 13, 1965 T. R.scHuERGER ETAL 3 Sheets-Sheet 2 nv vf/v mns n10/ms n. scf/afnam and FRA/v/r SLAM/m Alfarney AJully 13, 1965 I T. R. SCHUERGER ETAL l 3,194,546

MECHANISM AND METHOD FOR CONTROLLING SI'NTERING Filed Aug. 29. 1958 3Sheets-Sheet 3 Re/ay B A j Y Energ/Zed I- I- Deanery/'Zed 'MeasuringT/me /NVENTORS THOMAS R. scm/5R65? and FRANK SLAl/l "0n Time Timer .90I- L I 2 g i- 'Off Time" Harney United States Patent O 3,194,546MECHANISM AND METHOD FOR CGNTROLLING SlNTERING Thomas R. Sehuerger andFrank Siamar, Monroeville,

Pa., assiguors to United States Steel Corporation, a corporation of New.lersey Filed Aug. 29, 1958, Ser. No. 758,166 17 Claims. (Cl. 266-21)This invention relates to an improved mechanism and method forcontrolling la sintering operation.

In a conventional traveling grate sintering machine, a carefullyproportioned combustible mix of metal-bearing particles (for exampleiron ore), fuel and water feeds to the grate adjacent its entry end. Theupper surface of the resulting bed is ignited shortly beyond the line offeeding. Air is drawn or forced downwardly through the bed, andcombustion proceeds in a thin zone which slopes downwardly from the lineof ignition to a line along the grate, known as the burn-through point.For eflicient operation the location of the burn-through point must becarefully controlled. If the burn-through point lies too near thedischarge end of the grate, the finished sinter contains unburned fueland is of poor quality. If it lies too far from the discharge end, thefull capacity of the machine is not utilized. The location of theburn-through point is a function of grate speed, the rate at which thematerial burns, and the rate at which material feeds to the grate. Anearlier application of George Dykeman jointly with the presentcoinventor Schuerger, Serial No, 602,859, filed August 8, 1956 (nowPatent No. 2,878,003), discloses and claims an indicator for determiningthe actual location of the burn-through point. Our earlier applicationSerial No. 724,688, filed March 28, 1958 (now Patent No. 3,149,- 192),discloses and claims an apparatus and method for controlling the gratespeed to hold the burn-through point at a set location as determined bythis indicator.

Conventionally the ingredients of a sinter feed are brought together ina compounding apparatus which includes a main conveyor belt, a series ofbins located above the belt and containing the individual ingredients,and table feeders for feeding these ingredients in controlled quantitiesto the belt. Several bins farthest from the discharge end of the beltusually contain ore fines and equivalents. The next bins usually containfuel (for example coke and anthracite nes) and other additives. The binnearest the discharge end usually contains hot fines returned from thesintering machine for recycling. These lines, known as hot recycle, areanother equivalent of ore and must be used approximately as received,except that the bin allows suicient surge capacity to permit theirfeeding at uniform rates for extended periods. An earlier application ofthe present co-inventor Schuerger Serial No. 579,326, filed April 19,1956, discloses and claims a control method and means applicable to theforegoing type of feed compounding apparatus for automaticallyproportioning additives and Water in accordance with the combined weightof ore and Vhot recycle, even though hot recycle reaches the belt afterthe additives. When a change is needed in the hot recycle feed rate, acompensating inverse change first is made in the ore feed rate, wherebythe sum of these rates remains constant. Compensating changes in the orefeed rate can be made either by automatic or manual adjustment. Ineither event the constant sum can be adjusted to regulate the weight ofsintered feed produced. The assembled ingredients discharge from thebelt to a mixer where Water is added, and thence feed to a sinteringmachine.

Application Serial No. 579,326 was abandoned with 3,l9d,5ll6 Patentedjuly 13, 1955 ice the filing of a continuation-impart Serial No.810,508, which issued as Patent No. 2,980,291, April 18, 1961.

The present invention concerns a control mechanism and method in whichthe weight of material fed to the grate is adjusted automatically tohold the burn-through point at any set location. The grate speed adjustsitself automatically to maintain the depth of bed on the grate within apredetermined range despite varying feed rates. Whenever it is desiredto shift the burn-through point to a different location, the setting canbe changed, Whereupon both the feed rate land grate speed automaticallychange accordingly. This invention makes use of a burnthrough indicatoron the sintering machine and controls on the feed compounding apparatussimilar to those shown in the foregoing applications, plus suitablecomputing circuits, whereby the burn-through location directly controlsthe sum of the rates at which ore and hot recycle feed in thecompounding apparatus. In part these circuits are like those shown inour earlier application Serial No. 724,688, except now We control thefeed rate directly in accordance With burn-through location and Wecontrol grate speed to maintain the depth of the resulting bed on thegrate within a predetermined range. In the feed compounding apparatus wealso utilize a control for automatically maintaining the level of hotrecycle in its bin Within a predetermined range, as shown in our earlierapplication Serial No. 739,870, filed lune 4, 1958 (now Patent No.2,997,205), and preferably an automatic control for the ore feed rate asshown in our earlier application Serial No. 746,261, iled July 2, 1958(now Patent No. 2,965,265).

An object of the present invention is to provide fully automatic controlof a sintering operation, whereby both the rate at which material feedsto a sintering machine and the grate speed adjust themselvesautomatically to values that hold the burn-through point at any desiredlocation and maintain the depth of bed on the grate within apredetermined range.

A further object is to provide an improved mechanism and method forcontrolling a sintering operation in which the only manual adjustmentsare in setting the location of the burn-through point on the grate andin setting the proportions of additives and water, all other variablesbeing automatically controlled for optimum eiciency in accordance withthe setting of the burn-through location.

A further object is to provide an improved mechanism and method in whichthe controls shown in the aforesaid applications are combined to affordcompletely automated control of a sintering operation.

A more specific object is to provide an improved control mechanism andmethod for a sintering operation in which a burn-through indicator on asintering machine is connected through a suitable feed rate computingcircuit with an ore feed control on a feed compounding apparatus,whereby the circuit automatically regulates the weight of sinter feedproduced and fed to the sintering machine to hold the burn-through pointat a set location, and in which the grate speed is automaticallyregulated to maintain the depth of bed on the grate Within apredetermined range.

In accomplishing these and other objects of the invention we haveprovided improved details of structure, a preferred form of which isshown in the accompanying drawings, in which:

FIGURE 1 is a diagrammatic side elevational view of a sinteringinstallation equipped with control mechanism in accordance with ourinvention;

FIGURE 2 is a schematic showing of our feed rate computing circuit, thetimer circuit being omitted to simplify the illustration;

FIG. 3 is a schematic Wiring diagram of the timer y, 3 circuit for thecomputing circuit shown in FIGURE 2;

FIGURE 4 is a graph showing the sequence of operation; and

FlGURE 5 is-a schematic showing of our grate speed control mechanism.FIGURE 1 shows diagrammatically a sintering installation which includesa feed compounding apparatus 10, a mixer 12, and a traveling gratesintering machine 13, all conventional apart from our control mechanism.The compounding apparatus comprises a suitably driven main conveyor belt14, a plurality of ore bins 15, two trimmer ore bins 16, two additivebins 1'7, `and a hot recycle bin 18. The bins 15, 16, 17 and 13areequipped with table feeders 19, 20, 21 and 22 respectively which havevariable speed D.-C. drive motors 23,. 24, 25 and 26. Thus therespective ingredients feed from the bins to the belt in quantitiesindividually controlled by regulating the speeds of theY table feedermotors. 'sembled ingredients to the mixer 12 (for example a pug mill)where water is added via a line 27. A conveyor belt 28 carries theresulting sinter mix to the sintering machine 13 where it forms a bed S.The sintering rnachine comprises a traveling grate 29, a variable speedD.C. motor 31 for driving the grate, and an ignition device 32. Motor 31is equipped with a speed control mechanism 33 actuated by low and highlevel sensing means 34 and 35 mounted adjacent the feed end of thegrate. The control mechanism 33, hereinafter fully described,automatically maintains the grate speed at a value such that the beddepth remains within a range defined by the two sensing means regardlessof the feed rate. The sintering machine also includes the usualwindboXes, blowers, and otherconventional parts, but they are not shownsince they are not involved in the present invention.

The feed compounding apparatus is equipped with controls essentiallylike those shown in Schuergerapplication Serial No. 579,326, except wehave added an automatic control mechanism 36 for motor 26 which drivesthe hot recycle feeder 22, an automatic control mechanism 37 formotors24 which drive the trimmer ore bin feeders 2t), and a reset mechanism 38for motors 23 which drive the feeders 19 from the other ore bins. Thecontrol mechanism 36 is like that shown in our application Serial No.739,870, and the mechanisms y37 and 38 like those shown tin ourapplication Serial No. 746,261. The sintering machine is equipped with aburn-through indicator 39 like that shown in the Dykeman and Schuergerapplication. Hereinafter we explain how these devices operate insufficient detail to Yimpart an Yunderstanding of the present invention,but in the interest of conciseness we do not repeat detaileddescriptions of individual parts and circuits which appear in theaforesaid applications, and the drawings show these devices only inblock diagram.

The rate at which ore feeds to belt 14 from bins 15 and 16 is controlledthrough three signals proportionate to (a) the desired sum of the oreand hot recycle feed rates,

(b) the total weight of ore actually fed to belt 14, and (c) the rate atwhich the hot recycle feeder is set to operate. Voltages representativeof these signals are transmitted to the control mechanism 37 for thetrimmer -bin feeder motors 24. As shown in application Serial No.746,261, the mechanism is a magnetic amplifier in which voltagesrepresentative of signals (b) and (c) oppose the voltage representativeof signal (a). Motors 24 run at a speed proportionate to the resultantvoltage. In accordance with the present invention, signal (a) iscomputed periodically by a feed rate computing circuit 40 'controlled bythe burn-through indicator 39. This cir- Vcuit operates on similarprinciples to that shown in our application Serial No. 724,688, butsince the present tinvention utilizes the signal differently, thecircuit is described in detail hereinafter. Signal (b) is derivedcontinuously from a belt scale 41 of conventionalconstruction over whichbelt 14 passes after the ore has fed thereto.

The ore feed rate is regulated to maintain the sum of the ore feed rateand the hot recycle setting at a value determined by signalA (a). Thesum remains constant between successive computations of this signal. Anychange in signals (a) or (c) necessitates .a change in the ore feedrate. As long as only routineadjustments .are

Y needed in the ore feed rate, the` control mechanism 37 The beltdischarges the asp continuously regulates the speed of motors 24 yandhence changes only the rate at which ore feeds from the trimmer bins`16. NormallyV motors 23 run at constant speed, whereby ore feeds at aconstant rate from the other bins i 15.v When an unusually largeadjustment is needed in the ore feed rate, the control mechanism 37actuates the reset mechanism 38. Thereupon the reset mechanismperiodically changes the speed of motors 23 until the feed rate frombins 15 reaches a value at `which the trimmer bins alone can handlenecessary adjustments intheV total ore feed rate. Occasionally theweight of ore reaching belt 14 may change even though the speed of thefeeder motors 23 and 24 does,not'change. The resulting change in signal(b) immediately corrects the speed of motors 24 accordingly. Y

Periodically the hot recycle control mechanism 36 computesa new speedfor motor 26, which drives the feeder 22 on the hot recycle bin 18. Ifthe level of hot recycle 1in the bin is within a predetermined range,the new speed equals the instant speed, or the linstant speed with atemporary increment discontinued. 1f the level is outside the range, thenew speed equals the` algebraic sum of the instant speed, a temporaryincrement (positive or negative) to return the level to thepredetermined range, and a permanent increment (positive or negative) tohold the level within this range after it has returned. Signal (c) isrepresentative of the computed new speed. VIf the new speed differs fromthe instant speed, the control mechanism 37 immediately changes the orefeed rate linversely to the change indicated lin the hot recycle feedrate, and thus maintains the sum at the value Vdetermined by signal (a).After a delay sufficient for belt 14 to carry the changed quantity ofore oppositethe hot recycle bin 13, the computed new speed is appliedtormotor 26. Belt 14 runs over conventional belt scales 42 and 43immediately before and after hot recycle feeds thereto.

-The difference in weights which these scales register represents theactual weight of hot recycle fed to the belt. The scales are connectedto an algebraic summator 44 which continuously determines thisdifference. The result is Vapplied to the control mechanism 36 forcalibration purposes.

Signals (b) and (c), representative of the actual Weight tof ore and thehot recycle setting, .also are transmitted to a summator 48, whichcontinuously determines their sum, as in the :apparatus shown inSchuerger application Serial No. 579,326. .This summat-or transmits asignal vproportionate to said :total to ratio devices 49, which regulatethe Spee-d of motors 25 :driving the additive feeders V21, and toanother natio device 50, which regulates `a valve 51 in the water line27. These ratio devices are individually adjustable, whereby additivesand water can be included in any desired ratio with respect to the sumof the ore land hot recycle. The Schuerger application cites speci-ticexamples of known instruments suitable as sure signal through a suitabletransducer, such as that shown in a printed publication by the FoxboroCompany, Foxboro, Massachuetts, Bulletin 20-16 entitled E.M.F. PneumaticTransmitter.

Feed rate computing circuit FIGURE 2 shows the t'eed rate computingcircuit 40 in more detail, apart from its timer circuit shown separatelyin IF`IGURU'1`J 3. Periodically the circuit 40 acts in conjunction withthe burn-through indicator 39 to determine whether .the burn-throughpoint actually is at the location .to which it has been set, yand ifnot, to compute -a new feed rate to shift burn-through point tothe setlocation. If the burn-through point lies too far from the discharge endof the grate, the feed rate is increased; if it lies ltoo near thedischarge end, the feed rate is decreased. The circuit 40 exercisesdirect control only Iover the su-m of the ore and hot recycle feedrat-e, but this sum is representative of the total feed rate, since theadditives are proportioned :directly in accordance therewith.

The b-urn-through indicator 39 includes a servomotor (designated 30 inthe Dyketman and Schuerger :application) which is mechanically connectedto the arm 52 of a potentiometer 53. Thus .the indicator 39 positionsthis arm `along the potentiometer slide Wire in accordance with theactual distance L between the ignition point :and the burn-throughpoint. A manually .adjustable set-point -indicator 54 is mechanicallyconnected to the varm 55 of another potentiometer 56 to position thisarm along the potentiometer slide Wire in accordance with Ithe setdistance L between the same ignition point and the burnthrough point.The respective slide wires are connected to .suitable D.C. voltagesources, whereby arms 52 and -55 transmit voltages proportionate to LandL0 respectively.

Arms 52 and 55 are :electrically connected to a divider 57, whichcomputes -any variance between the actual and set locations of theburn-through point las Ia ratio LO/L. The divider includes .anelectronic conversion amplifier 58, :a servomotor 59 and a potentiometer60 whose arm 61 is mechanically connected to the servomotor. Arm `55 iselectrically connected to one input terminal of the amplier, whereby thevoltage applied to this terminal is proportionate to L0. Arm 52 iselectrically connected to one end of :the slide Wire of potentiometer l,.an-d `arm 61 of the latter .potentiometer is electrically connected tothe other input terminal of the amplifier. Thus the voltage applied tothe 'latter terminal is proportionate to L multiplied by a fractionwhose value depends on the linear position of arm .61 with respect toits slide wire. Amplifier `58 .and servomotor 59 are electricallyconnected to a suitable A.C. source 62. The output terminals of ampliierS are 'electrically connected to a field winding 63 of the serv-omotor.Amplifier 58 has the characteristic that it energizes the serv-omotor inthe appropriate direction Whenever its two input terminals .are yatdifferent voltages. When the servornotor runs, it moves arm 61 .alongits slide wire in a direction to equalize the voltages applied lto theinput terminals. -When these voltages become eq-ual, the servomotorstops and the linear position of arm .61 with respect to its slide wire.aiiords a measurement of the natio Lo/L. This computation can be madecontinuously, Ibut it is iused only periodically. We prefer not .tooperate the equipment unnecessarily; therefore we include front contactsA1 of 'a relay A in series with the servomotor. The relay itself is partof the timer circuit hereinafter described, and it automatically closesthese contacts whenever a computation is to be made.

The Vamplifier 58 per se is ta known device and hence has been shownonly in block form, but reference can be made to Wills Patent No.2,423,540 for a complete showing of :a suitable amplifier of this type.A suitable arnplier is available commercially from Minneapolis-Honeywell Regulator Company runder the tradename Electronik, No.356,358, and is described in a printed publication by the manufacturerentitled Service Manual 6 SO M for Class 15 Electronik InstrumentsIIssue 8 .'The servomotor 59 of the divider 57 also is mechanicallyconnected `to the arm 64 of a potentiometer 65. The slide Wire of thispotentiometer is connected to a D.-C. voltage source which applies lavoltage proportionate to the instant feed rate F .of material to grate29, as hereinafter explained. Arm o4 assumes a position in accordancewith the ratio Lo/L, whereby it transmits la voltage proportionate tothe product FLO/L. Iif there were no minor uctuations to consider, thecorrected feed rate F0 would equal this product, since the corrected.rate F0 bears the same ratio to the actual rate iF as the set distanceL0 between .the ignition point and ythe burn-through point bears to theactual distance L, that is However, we preferably apply the Voltagetransmitted by arm 64 to an integrator 66 for the purpose of computingan average value of FLO/L over a definite time interval and thuseliminating effects of minor fluctuations or noise in the measureddistance L.

The integrator includes an electronic conversion ampliher 67 (similar toamplifier 58), a servomotor 68, and a tachometer-generator 69mechanically connected to the servomotor. The servomotor is a two-phaseA.-C. induction motor which has the characteristic that under transientconditions its speed varies with the voltage applied to its iield. Wehave not described the motor in detail since it is a known device, butfor a complete description reference can be made to Thaler and BrownServo-Mechanisms Analysis, copyright 1953 by McGraw-Hill Book Company,Inc., pages 63 and 391. One input terminal of ampliier 67 iselectrically connected to arm 64 of potentiometer 65, whereby thevoltage applied to this terminal is proportionate to FLO/L, but subjectto fluctuations. The other input terminal of the ampliiier iselectrically connected to the generator 69, whereby the voltage appliedto the latter terminal is proportionate to the output of the generator.The voltages applied to the two input terminals are of the samepolarity, but the latter is smaller. Ampliiier 67 and servcmotor 63 areelectrically connected to a suitable A.C. source 70. The outputterminals of amplier 67 are electrically connected to a iield winding 71of servomotor 68. Front contacts A2 of relay A are connected in serieswith servornotor 68, and are closed automatically by the timer circuitfor a definite interval,

for example one minute, when a computation is to be made. It should bepointed out that the integrator o6 is not a null-seeking device like thedivider 57, but voltages applied to its two amplifier input terminalsapproach values which differ by an amount proportionate to the voltageto be integrated. The amplifier 67 allows the servomotor 63 to run aslong as contacts A2 remain closed.

The action of the integrator can be explained mathematically as follows:

Let y el represent the input voltage to the amplifier proportionate toFL/L;

e2 represent the input voltage to the amplifier derived from thetachometer-generator;

t represent the time interval the servomotor runs for each computation;and

x represents the number of revolutions of the tachometergenerator duringtime t.

Then

(e2-e1) is the eitective voltage which tends to drive the servomotor;and

lx/dt is the angular velocity of the tachometer-generator.

Thus it isseen that x is a function of e1, and measurement of x over adefinite time interval can be used to obtain a measurement of an averagevalue of el or FLO/L for the same interval. The tachometerugenerator 69is mechanically connected to the arm 7270i a potentiometer 73 throughsuitable reduction gearing. Consequently the distance which the armtravels during time interval t furnishes a measure of the number ofrevolutions x during this interval. The slide wire of potentiometer 73is electrically connected to a suitable D.C. voltage source, whereby arm72, transmits a voltage proportionate to thecomputed average value ofFLO/L during the interval t. This value is taken as F0, the correctedfeed rate.

After the computed value F has been utilized, as herefe1dt-l- Constant-inafter explained, the potentiometer arm 72 is reset to its zeroposition. For this purpose, the connection between arm 64 and the firstinput terminal of amplifier 6^? contains a contact B1 of a relay B andthe connection between the generator 69 and the other input terminal ofthe amplier contains a contact B2 of relay B, which contacts are closedwhile the integrator is performing a computation. A contact B3 of relayB is adapted to connect the irst input vterminal to a ground '74. Acontact B., of relay B is .adapted to connect the other input terminalto arm 72 of potentiometer '73. Additional contacts B5 of relay B areadapted to connect servomotor 68 to the A.C. source 7GB, bypassingcontacts A2. Contacts B3, B and B5 are open while the integrator isperforming a computation. Relay B itself is part of the timer circuithereinafter described. When the potentiometer arm is to be reset,contacts B1 and B2 open and contacts B3, B4 and B5 close. The servomotorV58 runs in the reverse direction until the voltages applied to the twoinput terminals of the amplifier 67 are equal. Since one terminal isgrounded at 74, these voltages become equal when the other terminal isgrounded, that is, when the potentiometer arm 72 reaches its zerosetting. The integrator in effect becomes a null-seeking device while itis resetting the arm.

Before the arm 72 is reset, the voltage which it transmits proportionateto F0 is applied to a memory device 75. The memory device includes `anelectronic conversion amplier 76 (similar to amplifiers 58 and o7), aservomotor 77, and a potentiometer 78 whose arm 79 is mechanicallyconnected to the servomotor. The slide wire of potentiometer 78 iselectrically connected to a suitable D.C. source. Arm '72 iselectrically connected to one input terminal of amplifier 76, wherebythe voltage applied to this terminal is proportionate to F0. Arm 79 iselectrically connected to the -other input terminal of the ampliiier,whereby the voltage applied to this terminal equals that applied to theslide wire of potentiometer 78 multiplied by a fraction whose valuedepends on the linear position of arm 79 with respect to the slide wire.

`Amplifier 76 and servomotor 77 are electrically connected to a suitableA.C. source 80. The output terminals of amplifier 76 are electricallyconnected to a field winding 81 of the servomotor. The action of thememory device is similar to that of the divider 57; that is, theservomotor 77 stops after moving arm 79 to a linear position along itsslide wire representative of the computed value Front contacts C1 of arelay C are connected in the A.C. circuit S0. The relay itself is partof the timer circuit hereinafter described. Y Contacts C1 automaticallyclose long enough to enable the servomotor 77 of theV memory device toset theY potentiometer arm 79 to the new value of F0 computed by theintegrator. Thereafter these contacts reopen to hold the arm`at thissetting until another new setting is computed.

Theservometer 77 of the memory device 75 also is mechanically connectedto the arm 82 of a potentiometer 83, which is electrically connected toa suitable D.C. source. Arm S2 thus assumes a position in accordancewith the computed value of F0, and transmits a'proportionate Voltage.Arm 82 is electrically connected to the trimmer bin control mechanismand transmits signal (a) thereto. As already explained the total feedrate bears a known ratio to the sum of the ore and hot recycle feedrates; hence the computed value of Fo also is representative of thissum. The potentiometer arm 82 also is electrically connected to theslide wire of potentiometer 65 and transmits a voltage thereto tobe'used as For the instant feed rate in the next computaion.

Toshift the burn-through point intentionally, it is necessary only tomove the set-point indicator to a new position of adjustment. Thereuponthe circuit 4t) computes a new feed rate which shifts the burn-throughpoint to vthe new setting and holds it there after it vhas been shifted.'If it is desired to operate the sintering machine at less than fullcapacity, it is only necessary to set the location of the burn-throughpoint farther from the discharge end of the grate. 2 i Y Manualadjustment ,and connects potentiometer 84 to the memory device,

whereby the voltage applied tothe memory device can be set manuallythrough potentiometer 84. Circuit to thev servomotor 77 of the memorydevice contains front contacts D3 which close when relay D is energized.The memory device transmits a signal for regulating the trimmer bincontrol mechanism 37 the same as when the automatic control means isconnected.

Timer circuit FIGURE 3 is a schematic wiring diagram of a preferredtimer circuit. In addition to the relays A, B, C and D alreadymentioned, the circuit includes another relay E, two interval timers and91, and a switch 92 for setting the control to manna or automaticaTimers 90 and 91 are of a type which have an adjustable Volt-time and anadjustable on-time that repeat as long as the timer is running. Suchtimers per se are known and are available commercially; hence nodetailed showing is deemed necessary. However, reference can he made toa printed publication of General Electric .Company entitled TSA-18Industrial Interval Timer for a complete showing and description.Thecircuit is energized from two lines 93 and 94 connected to a suitablevoltage source. Switch 92 and theV coil of relay D are connected inseries across lines 93 and 91%. Forautomatic operation the switch isopen and the'relay deenergized, and for manual openation the reverse.Relay D has a back contact D4 which connects the other relays and thetimers to line 93 as long as relay D is deenergized, but breaks thisconnection when the relay is energized.

Timer 90 runs all the while the control is set for automatic operation.It has Va contact 90a which opens during its off-time and closesduringits on-time. The on-time defines the interval t, hereinbeforereferred to,

- during which a corrected feed rate Ff, is computed. Conf 9 relay Apicks up, its front contacts A1 and A2 close to operate servomotors 59and 63 of the divider 57 and integrator 66 respectively, as alreadydescribed. The coil of relay E, a front contact A3 of relay A, and aback contact C2 of relay C lare connected in series across lines 93 and$4, whereby relay E picks up with relay A. Relay E has a front contactE1 through which it seals in, bypassing contact A3. The coil of relay B,a back contact E2 of relay E, and a back contact C3 of relay C areconnected in series across lines 93 and 94, whereby relay B is normallyenergized, but drops out when relay B picks up. When relay B drops out,contacts B1 and B2 close to apply the voltages from arm 64 ofpotentiometer 65 and from the tachometer-generator 69 to the inputterminals of the amplifier 67 of the integrator; contacts B3 and B4 opento break the connections to the ground 74 and to the arm 72 ofpotentiometer 73. Contacts B5 open so that the servomotor 68 can beenergized only via contacts A2. Since relay B is normally energized,FIGURE 3 shows contacts B1 and B2 open even though they actually areback contacts, and contacts B3, B4 and B5 closed even though theyactually are front contacts.

Another front contact A.; of relay A and timer 91 are connected inseries across lines 93 and 94, whereby timer 91 is energized when relayA picks up. Timer 91 does not run continuously like timer 99, but is setto operate through only a single cycle of ott-time and onetime wheneverit is energized. Otherwise any synchronization errors in the timerswould be cumulative, and soon would upset the sequence of operations.Timer 91 is also connected to line 93 through a conductor 95 and remainsenergized through this conductor after relay A drops out. The on-time oftimer 90 ends an instant before the on-time of timer 91 commences. Whenthe n-time of timer 90 ends, contact 90a opens, relay A drops out, andservomotors S9 and 63 stop. When the on-time of timer 91 commences, thetimer closes a contact 91a which is connected in series with the coilofrelay C across lines 93 and 94. Relay C picks up and closes itscontacts C1 to operate the servomotor 77 of the memory device 75. Aslong as relay D remains deenergized, the amplifier 76 of the meinorydevice remains connected to arm 72 of potentiometer 73. The on-time oftimer 91 is sufficient that the servomotor 77 operates long enough toset the memory device to the corrected feed rate F0. Subsequently timer91 is deenergized, whereupon contact 91a opens, and relay C drops out.

When relay C picks up, its back contacts C2 and C3 open. Opening ofcontact C2 drops out relay E, but opening of Contact C3 for the momentprevents relay B from picking up. When relay C drops out, relay B picksup, whereupon its contacts B3 and B4 connect the amplifier 67 of theintegrator to ground 74 and to the potentiometer arm 72, and itscontacts B energize the servomotor 68. Thus the potentiometer 73 isreset. It should be noted that relay B cannot be energized until bothrelays A and C are deenergized; consequently, the potentiometer 73 canbe reset only when resetting does not interfere with other operations.

When our control is operated manually, switch 92 is closed and relay Dpicks up. Contacts D1 and D4 open,

vwhereby the electrical connections are broken between the potentiometerarm 72 and ampliiier 76 of the memory device 75 and between line 93 andthe timer 90. Contact D2 closes and establishes a connection between themanually operated potentiometer 84 and amplifier 76. Contacts D3 closeand establish a connection between the A.C. circuit 80 and theservomotor 77 of the memory device. The way in which the memory devicecan be set -manually with the contacts in these positions has already'been explained.

Operating sequence FIGURE 4 shows a typical sequence diagram for ourfeed rate control mechanism when set for automatic operation. Initiallytimer 9e) is running but is registering ofi-time, timer 91 is stopped,and relay B is energized. Thus no computation is taking place and relayB maintains the integrator 66 and potentiometer -arm 72 in a reset orzero position. Presently the on-time of timer 91) commences. The timercircuit already described drops out relay B and starts timer 91, whichat iirst registers ott-time. The divider 57 and integrator 66 now maketheir computation of a corrected feed rate, and potentiometer arm 72 ispositioned accordingly. After an interval t the on-time of timer endsand the timer goes back into oft-time. An instant later the on-time oftimer 91 commences, but relay B remains deenergized. The potentiometerarm 72 remains positioned in accordance with this computed feed ratewhile the memory device '75 positions the potentiometer arm 82accordingly.

ignal (a) and the ore feed rate are corrected simultaneously with thepositioning of arm 82. Subsequently the on-time of timer 91 ends andthis timer stops. Relay B picks up to reset the potentiometer arm 72,but the potentiometer arm 82 retains its setting until a new computationis made.

The interval between computations should approximate the time requiredfor a particle to travel from the trimmer bins 16 to the discharge endof grate 29, typically about 4S minutes. The duration of a computationshould be suiiicient to furnish a representative average of conditionsprevalent on the grate, typically about 1 to 2 minutes. The interval forsetting the memory device should be long enough only for the parts toreach their computed positions, allowing a reasonable margin, typicallyabout 15 to 30 seconds. Thus timer 90 can be set for about 45 minuteso-time and about 1 to 2 minutes on-time, and timer 91 for oit-time aninstant longer than the on-time of timer 90 and about 15 to 30 secondson-time.

Grate speed control mechanism FIGURE 5 shows the grate speed controlmechanism 33 in more detail. This mechanism comprises a speed computingcircuit 98 and a motor control 99. Whenever the bed depth is outside thedesired range, the speed computing circuit 98 computes a new grate speedwhich equals the algebraic sum of the instant speed, a temporaryincrement (positive or negative) to return the depth to the desiredrange, and a permanent increment (positive or negative) to hold it inthe desired range after it has returned. Both increments are of coursenegative when the bed is too shallow and positive when it is too deep.After the increments are applied to the motor speed and the bed depthreturns to the desired range, the circuit 98 computes another new speedwhich equals the instant speed with the temporary incrementdiscontinued. The speed computing circuit 98 acts periodically, but itscycle is short (for example 5 seconds computing and 5 seconds betweencomputations), whereby the mechanism etlectually exercises continuouscontrol over the grate speed.

The speed computing circuit 98 is energized through lines 1110 and 161connected to a suitable D.C. source. The low level sensing means 34controls a contact 34a which is connected across these lines in serieswith the coil of a relay H. The high level Sensing means 35 controls acontact 35a which is connected across these lines in series with thecoil of a relay 1. Whenever the bed S becomes too shallow to actuateeither sensing means 34 or 35, both contacts 34a and 35a open and bothrelays H and .l are deenergized. When the bed depth is within thedesired range and actuating the low level sensing means 34, contact 34acloses and relay H picks up. Whenever the bed becomes so deep that itactuates both sensing means 34 and 35, both contacts 34a and 35a closeand both relays H and .l pick up.

Relays H and I control a pair of relays K and L, which in turn controlthe application of negative and positive temporary speed changeincrements respectively. The

coil of relay K is connected acrosslines '100 and 101 in series with aback contact H1 of relay H and a front contact T1 controlled by a timerT. Similarly the coil of relay L is connected across these lines inseries with a front contact J1 of relay I and a front contact T2 of thetimer. Timer T automatically and periodically opens and closes itscontacts for brief intervals. If the bed depth is within the desiredrange when the timer closes its contacts T1 and T2, neither relay K norL picks up, since both contacts H1 and J1 remain open. If the bed istooshallow, relay K picks up with the closing of timer contact T1, sincerelay H is deenergized and its contact H1 closed. Similarly if the bedis too deep, relay L picks up with the closing of timer contact T2,since relay J is energized and its Contact I1 closed. Whenever eitherrelay K or L picks up, it seals in via back Contact T3 or T., of thetimer and its own front contact K1 or L1. Relays K and L are relativelyslowacting to enable them to remain energized during the intervalcontacts T1 and T2 are opening and contacts T3 and 'T4 closing. After atemporary increment in the speed returns the ned depth to the desiredrange, contact H1 or I1 immediately opens. The next time timer T opensits contacts T3 and T4, relay K or L drops out and the temporaryincrement is discontinued.

' Relays H and J also` control a reversing motor 102 which in turncontrols the application of permanent speed change increments. Thismotor is connected across lines 100 and itil in series with backcontacts H2 and H3 of relay H and front contacts T5 and T6 of timer Tfor energizing it in one direction, and in series with front contacts I2and J3 of relay l' and the same contacts T5 and T5 for energizing it inthe opposite direction, If the bed depth is within the desired rangewhen timer T closes its contacts T 5 and T6, the motor does not operate,since contacts H2, H3, I2 and J3 are all'open. If the bed is tooshallow, the motor runs in a direction to apply a negative increment,since relay H is deenergized and contacts H2 and H3 are closed.Similarly if the bed is too deep, the motor runs in the oppositedirection to apply a'positive increment, since relay J is energized andcontacts J2 and I3 are closed. In either event the motor stops whentimer T opens its contacts T5 `and T6, thusk limiting the magnitude ofthe permanent increment.

The circuit vincludes a potentiometer 163 whose slide wire is connectedto a suitable D.C. source for developing a speed controlling voltage.The potentiometer has an arm Illdwhich is electrically connected to anoutput terminal 105 via two variable resistances 106 and 107 in series,

and is mechanically connected to motor 102. A back in parallel withresistance 107. When relay L picks up as a result of an excessively deepbed, contact L2 closes and shunts out the latter resistance.Consequently the voltage transmitted to the terminal rises to effect apositive temporary speed increment. The magnitude of temporaryincrements can be adjusted by adjusting resistances 106 and T07. Whenmotor 162 runs, it moves arm 104 along the slide wire in a direction tolower or raise the voltage transmitted to the terminal to effect anegative or a positive permanent speed increment. The magnitude ofpermanent increments can be adjusted by adjusting the llength of timethe motor runs. The ultimate voltage on `the output terminal T05 isLproportionate to the most recently computed speed for motor 3l and istransmitted to the motor control 99.

The motor control 99 illustrated includes a motor-generator 108 and amagnetic amplifier 169 which has Aa control winding 110. The magneticamplifier and motor por- `VVtion of the motor-generator are connected tosuitable fn-C. sources. 1Terminal 1.05 of thespeed computing circuit iselectrically connected tothe Winding 1141i and continuously transmitsthereto a voltage proportionate to the most recently computed speed formotorfil.` The magnetic amplifier isconnected to a lield winding i12 ofthe D.C. generator, whereby the voltage appliedrto the field winding,and hence the voltage output of the generator, vary with the voltageapplied to the control winding llt). The generator is electricallylconnected lto the D.C. motor 31, whose speed thus is governed by thissame voltage. We have not described the magnetic ampliiier in detailsince it is a known device, but for a complete description reference canbe made t0 Storm Magnetic Amplifiers, Copyright 1955 by General ElectricCompany. An explanation of the way a magnetic amplifier can be used as avoltage regulator for a D.C. generator appears on pages 4l8rand 419 ofthis publication. Y

From the foregoing description it is seen that our invention affords afully automatic mechanism and method for controlling a sinteringoperation. Except for setting the desired proportions of additives andwater in the sinter mix, the only adjustment necessary is in setting thelocation at which it is desired to maintain the burn-through point.

The mechanism then automatically controls the feed rate and grate speedto hold theburn-through point at this location. Similar results can beattained by using the individual control devices shown in our otherapplications, ,except that it is necessary also to usel a surge binbetween the compounding apparatus and the sintering machine. The presentinvention overcomes any need for a surge bin,

.since the feed rate to the compounding apparatus is controlled directlyto produce the actual feed needed in the .sintering machine.

While we have shown and described only a single em- 'bodiment of theinvention, it is apparent that other modications may arise. Therefore,We do not wish to be limited to the disclosure set forth but only` bythe scope of the appended claims.Y

We claim:

l. In a sintering installation which includes a traveling gratesintering machine, apparatus for assembling and mixing ingredients of acombustible sinter mix and feed- Ying the mix to said machine, and aburn-through indicator -operatively connected with said machine, thecombination therewith of a control mechanism comprising computing meansoperatively connected with said indicator for computing feed rates -tohold the burn-through point at a set location on the grate, and meansoperatively connected with said computing kmeans Vand said'apparatus'for regulating the quantity of sinter mix fed Yto said machine `inaccordanceV with computed rates.

2. In a sintering installation which includes a traveling -gratesintering machine,apparatus for assembling and -mixing ingredients of acombustible sinter mix and feedance with computed rates, and meansoperatively connected with said'machine to regulatek the speed at which`its grate travels to maintain the depth of the .bed Within .apredetermined range.

3. In a sintering installation which includes a ,traveling Ygratesintering machine, apparatus for assembling and mixing ingredients toform a combustible sinter mixand 'feeding the mix to said machine, and aburn-through indicator operatively connected with said machine, thecomrbination therewith of a control mechanism comprising a ,set-pointindicator, computing means .operatively con- 751nected1with saidindicators for periodically computing 13 a new feed rate to shift theburn-through point from its actual location on the grate indicated bysaid burnthrough indicator to a set location indicated by said setpointindicator, means operatively connected with said computing means andsaid apparatus for regulating the quantity of sinter mix fed to saidmachine in accordance with computed rates, and timingr means operativelyconnected with said computing means `for regulating the period betweensuccessive operations thereof to approximately the time taken for mix ofcorrected feed rate to reach the discharge end of the grate.

4. A combination as defined in claim 3 in which said computing meansincludes means for averaging the computation of a new feed rate over asufficient period to eliminate effects of minor fluctuations.

5. In a sintering installation which includes a traveling gratesintering machine, apparatus for assembling and mixing ingredients of acombustible sinter mix and feeding the mix to said machine to form a bedon the grate thereof, and a burn-through indicator operatively connectedwith said machine, the combination therewith of a control mechanismcomprising a set-point indicator, computing means operatively connectedwith said indicators for periodically computing a new feed rate to shiftthe burn-through point of the bed from its actual location on the grateindicated by said burn-through indicator to a set location indicated bysaid set-point indicator, means operatively connected with saidcomputing means and said apparatus for regulating the quantity of sintermix fed to said machine in accordance with computed rates, timing meansoperatively connected with said computing means for regulating theperiod between successive operations thereof to approximately the timetaken for mix of corrected feed rate to reach the discharge end of thegrate, and means operatively connected with said machine to regulate thespeed at which its grate travels to maintain the depth of the bed withina predetermined range.

6. In a sintering installation which includes a traveling gratesintering machine, apparatus for assembling and mixing ingredients of acombustible sinter mix and feeding the mix to said machine, and aburn-through indicator operatively connected with said machine, thecombination therewith of a control mechanism comprising a set-pointindicator, a first computing means operatively connected with saidindicators for determining as a ratio any discrepancy between the actuallocation of the burn-through point on the grate indicated by saidburn-through indicator and the set location indicated by said set-pointindicator, a second computing means operatively connected with saidfirst computing means for periodically computing as an average over aperiod suicient to eliminate effects of minor fluctuations a new feedrate to shift the burn-through point from its actual location to its setlocation, means operatively connected with said second computing meansand said apparatus for regulating the quantity of sinter mix fed to saidmachine in accordance with computed rates, and timing means operativelyconnected with said second computing means for regulating the periodbetween successive operations thereof to approximately the time takenfor mix of corrected feed rate to reach the discharge end of the grate.

7. In a sintering installation which includes a traveling gratesintering machine, apparatus for assembling and mixing ingredients of acombustible sinter mix and feeding the mix to said machine to form a bedon the grate thereof, and a burn-through indicator operativelyrconnectedwith said machine, the combination therewith of va control mechanismcomprising a set-point indicator,

a first computing means operatively connected with said indicators fordetermining as a ratio any discrepancy between the actual location onthe grate of the burn-through point of the bed indicated by saidburn-through indicator p and the set location indicated by saidset-point indicator,

a second computing means operatively connected with said rst computingmeans for periodically computing as i4 Y Y an average over a periodsufficient to eliminate effects of minor fluctuations a new feed rate toshift the burnthrough point from its actual location to its setlocation, means operatively connected with said second computing meansand said apparatus for regulating the quantity of sinter mix fed to saidmachine in accordance with cornputed rates, timing means operativelyconnected with said second computing means for regulating the periodbetween successive operations thereof to approximately the time takenfor mix of corrected feed rate to reach the discharge end of the grate,and means operatively connected with said machine to regulate the speedat which its grate travels to maintain the depth of the bed within apredetermined range.

8. In a sintering installation which includes a traveling gratesintering machine, a compounding apparatus for assembling ore, additivesand hot recycle, means operatively connected with said apparatus forproportioning the rate at which additives are included in accordancewith the sum of the ore and hot recycle rates, and means for mixingmaterials assembled in said apparatus and feeding them to said machine,the combination therewith of a control mechanism comprising computingmeans operatively connected with said machine for computing feed ratesrequired to hold the burn-through point at a set location on the grate,and means operatively connected with said computing means and saidapparatus for adjusting the sum of the ore and hot recycle rates inaccordance with the computed feed rate.

9. In a sintering installation which includes a traveling gratesintering machine, a compounding apparatus for assembling ore, additivesand hot recycle, means operatively connected with said apparatus forproportioning the rate at which additives are included in accordancewith the sum of the ore and hot recycle rates, and means for mixingmaterials assembled in said apparatus and feeding them to said machineto form a bed on the grate thereof, the combination therewith of acontrol mechanism comprising computing means operatively connected withsaid machine for computing feed rates required to hold the burn-throughpoint of the bed at a set location on the grate, means operativelyconnected with said computing means and said apparatus for adjusting thesum of the ore and hot recycle rates in accordance with the computedfeed rate, and means operatively connected with said machine to regulatethe speed at which its grate travels to mainta-in the depth of the bedwithin a predetermined range,

w. In a sintering installation which includes a traveling gratesintering machine, a compounding apparatus for assembling ore, additivesand hot recycle, means operatively connected with said apparatus forregulating the rate at which hot recycle is included at substantiallythe rate received, means operatively connected with said .apparatus forproportioning the rate at which additives are included in accordancewith the sum of the ore and hot recycle rates, and means for mixingmaterials assembled in said apparatus and feeding them to said machine,the combination therewith of a control mechanism comprising computingmeans operatively connected with said machine for computing feed ratesrequired to hold the burn-through point at a set location on the grate,and means operatively connected with said computing means and saidapparatus for adjusting the ore rate to values at which the sum of theore and hot recycle rates is in accordance with the computed feed rate.

lll. In a sintering installation which includes a traveling gratesintering machine, a compounding apparatus for assembling ore, additivesand hot recycle, means operatively connected with said apparatus forproportioning the rate at which additives are included in accordancewith the sum of the ore and hot recycle rates, means for mixingmaterials assembled in said apparatus and feeding them to said machine,and a burn-through indicator operatively connected with said machine,the combination therewith of a control mechanism comprising a set-pointindicator, computing means operatively connected with said indicatorsfor periodically computing a new feed rate to shift the burn-throughpoint from its actual location on the grate indicated by saidburn-through indicator toa set location indicated by said set-pointindicator, means operatively connected with said cornputing means andsaid apparatus for adjusting the sum of the ore and hot recycle rates inaccordance with the computed feed rate, and timing means operativelyconnected with said computing means for regulating the period betweensuccessive operations thereof to approximately the time taken for mix ofcorrected feed rate to reach the discharge end of the grate.

, l2. A method of controlling a traveling grate sintering operationcomprising periodically computing rates of feeding material to the grateto shift the burn-through point from its actual location to a setlocation, changing the feed rate to the computed rate, and regulatingthe speed at which the grate travels to maintain the depth of materialthereon within a predetermined range.

13. In a sintering operation wherein ore, additives and hot recycle arebrought together, mixed and fed to a traveling grate sintering machineto form a bed on the grate thereof, a method of control comprisingperiodically computing a new feed rate to shift the burn-through pointof the bed from its actual location on the grate to a set location,changing the sum of the ore and hot recycle rates in accordance with thecomputed new rate, proportioning additives in accordance with this sum,the period between successive computing steps approximating the timetaken for material of a new feed rate to reach 'the discharge end of thegrate and regulating the speed at which the grate travels to maintainthe depth of the bed within a predetermined range.

I4. In a sintering installation which includes a travelinggratesintering machine, apparatus for assembling and mixing ingredientsof a combustible sinter mix and feeding the mix to said machine to forma bed on the grate thereof, and a burn-through indicator operativelyconnected with said machine for indicating the actual location of theburn-through point on the grate, the combination therewith of a controlmechanism comprising a set point indicator for indicating the desiredVlocation of the burn-through point, respective voltage sourcesoperatively connected with said indicators for developing a firstvoltage which varies with the actual location of the burn-through pointand a second voltage which varies with the desired location, a divideroperatively connected with said voltage sources for determining theratio of said voltages `and thus determining the magnitude of anydiscrepancy between the actual and desired locations, means fordeveloping a third voltage propor` tionate to the instant feed rate ofsinter mix to said sintering machine, multiplying means operativelyconnected with said last named means and said dividerfor developing afourth voltage proportionate to the" product of vsaid third voltage andsaid ratio and thus determining a corrected feed rate to shift theburn-through point t the desired location, means operatively connectedwith said multiplying means and said apparatusY for periodicallychanging the feed rate to the corrected value, and timing Vmeans forregulating the period between successive cor- `rections in the feed rateto approximately the time taken for mix of corrected feed rate toreachthe discharge end of the grate.

15. In a sintering installation which includes a travel- 'ling gratesintering machine, apparatus for assembling and mixing ingredients of acombustible sinter mix and feeding the mix to said machine to forma bedon the grate thereof, and a burn-through indicator operatively connectedwith said machine -for indicating the actual loca- Ftion of theburn-through point on the grate, the combination therewith of ,a controlmechanism comprising a set lrpoint indicator for indicating the desiredlocation of the burn-through point, respective voltage sourcesoperatively connected with said indicators for developing a firstvoltage which varies with theactual location of the burnthroughpoint anda second voltage which varies with the desired location, a divideroperatively connected with said voltage sources for determining theratio of said voltages and'thus determining the magnitude of anydiscrepancy between the actual and desired locations, means fordeveloping a third voltage proportionate to the instant feed rate ofsinter mix to said sintering machine, multiplying means operativelyconnected with said last named means and said divider for developing afourth voltage proportionate to the product of said third voltage andsaid ratio and thus determining a corrected feed rate to shift theburn-through point to the desired location, averagingmeans operativelyconnected with said multiplying means for developing periodically afifth voltage proportionate to said fourth voltage averaged over aninterval sufficient to eliminate' effects of minor liuctuations in theactual location, a memory device operatively connected with saidaveraging means and said apparatus for periodically changing and holdingthe feed rate at the corrected value until another corrected value isdetermined, and timing means operatively connected with said averagingmeans and said memory devicefor regulating the period betweenYsuccessive corrections in the feed rate toY approximately the time takenfor mix of corrected feed rate to reach the discharge end of the grate.

16. In a sintering installation which includes a traveling rgratesintering machine, apparatus for assembling and mixing ingredients of acombustible sinter mix and feeding the mix to said machine to form a bedon the grate thereof, andahum-through indicator operatively connectedwith said machine for indicating the actual location of the burn-throughpoint on the grate, the combination therewith of a control mechanismcomprising a set ,point indicator for indicating the desired location ofthe burn-through point, respective voltage-sources operatively connectedwith said indicators for developing a first voltage which varies withthe actual location of the burnthrough point and a secondY voltage whichvaries with the desired location, a divider operatively. connected withsaid voltage sources for determining the ratio of said voltages and thusdetermining the magnitude of any discrepancy between the actual anddesired locations, means for developing a third voltage proportionate tothe instant feed rate of sinter mix to said sintering machine,multiplying vmeans operatively connected with said last named means andsaid divider for developing a fourth voltage proportionate to theproduct of said third voltage and said ratio andthus determining acorrected feed rate to shift the burn-through point to the desiredlocation, an integrator operatively connected with said multiplyingmeans for developing periodically a fth voltage proportionate to saidfourth voltage averaged over an interval suiiicient to eliminate effectsof minor liuctuations in the actual -location, a memory deviceoperatively connected with said integrator and said apparatus forperiodically changing and holding the feed rate at the corrected valueuntil another corrected value has been determined, the means fordeveloping said third voltage being operatively connected Vwith saidmemory device, and timing means operatively Yconnected with saidintegrator and said memory device .for regulating the period betweensuccessive corrections 1n the feed rate to approximately the time takenformix of corrected feedV rate to reach the discharge end of the grate.g K v l 17. In a sintering installation which includes a travelmg gratesintering machine, apparatus for assembling and vmixing ingredients of acombustible sinter mix and feeding the mix to said machine Vto form abed on the grate thereof, and a burn-through indicatoroperativelyconnected with said machine for indicating the actuallocation of the burn-through point on the grate, the combinai? tiontherewith of a control mechanism comprising a set point indicator forindicating the desired location of the burn-through point, respectivevoltage sources operatively connected with sa-id indicators fordeveloping a first Volt age which varies with the actual location of theburnthrough point and a second voltage which varies with the desiredloc-ation, a divider operatively connected with said voltage sources fordetermining the ratio of said voltages and thus determining themagnitude of any discrepancy between the actual and desired locations,means for developing a third voltage proportionate to the instant feedrate of sinter mix to said sintering machine, multiplying meansoperatively connected with said last named means and said divider fordeveloping a fourth voltage proportionate to the product of said thirdvoltage and said ratio and thus determining a corrected feed rate toshift the burn-through point to the desired location, an integratoroperatively connected with said multiplying means for developingperiodically a fifth voltage proportionate to said fourth voltageaveraged over an interval sufficient to eliminate effects of minoriluctuations in the actual location, a memory device operativelyconnected with said integrator and said apparatus for periodicallychanging and holding the feed rate at the corrected value until anothercorrected value has been determined, the means for developing said thirdVoltage being operatively connected with said memory device, meansoperatively connected with said sintering machine for regulating thespeed at which the grate travels to maintain the bed depth within apredetermined range despite variations in the feed rate, and timingmeans operatively connected with said integrator and said memory devicefor regulating the period between successive corrections in the feedrate to approximately the time taken for mix of corrected feed rate toreach the discharge end of the grate.

References Cited by the Examiner OTHER REFERENCES The Iron Age, Oct. 9,1958, page 92,

MORRS O. WOLK, Primary Examiner.

RAY K. WINDHAM, NATHAN MARMELSTElN,

Examiners.

1. IN A SINTERING INSTALLATION WHICH INCLUDES A TRAVELING GRATESINTERING MACHINE, APPARATUS FOR ASSEMBLING AND MIXING INGREDIENTS OF ACOMBUSTIBLE SINTER MIX AND FEEDING THE MIX TO SAID MACHINE, AND ABURN-THROUGH INDICATOR OPERATIVELY CONNECTED WITH SAID MACHINE, THECOMBINATION THEREWITH OF A CONTROL MECHANISM COMPRISING COMPUTING MEANSOPERATIVELY CONNECTED WITH SAID INDICATOR FOR COM-